De-hardcode discovery from gittensory's own conventions

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Problem: Discovery and claim logic assumes gittensory's own labels, issue templates, and scoring rubric.

Area: AMS / Miner

Proposal: Work through #4780's checklist, turning each hardcoded assumption into per-tenant configuration with gittensory's own conventions surviving only as the default.

Deliverables:

• Discovery/claim code with no remaining hardcoded gittensory-specific assumption from the F2 checklist.

Acceptance criteria:

• Every item on the F2 checklist is either resolved or explicitly deferred with a reason.
• Existing behavior against gittensory's own repos is unchanged (regression-tested).

Test scenarios:

• Full existing miner test suite passes unchanged.
• A new test repo with different labels/templates is discoverable using its own configuration, not gittensory's defaults.

Resources:

• The miner package's discovery and claim modules.

Boundaries:

• Blocked on Repo-agnostic capability audit #4780.

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Part of #4778.

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JSO-3456